The proposed program of projects is comprised of several different areas of investigation having overlapping interests and many common experimental approaches. The projects have similar objectives in that they focus on the general area of mental retardation and other neurologic diseases, seeking improved diagnostic procedures, new therapeutic measures, and the elucidation of specific metabolic defects. These investigations encompass broadly the disciplines of biochemistry and genetics with specific projects ranging from basic to clinical in nature. Several different areas of metabolism, often interrelated, to be studied include carbohydrates, lipids, pyroles, mucopolysaccharides, amino acids, and trace metals. Specific disease entities being investigated include homocystinuria, congenital lactic acidosis, Menkes disease, acute intermittent and other porphyrias, lead intoxication, Krabbe's disease, leukodystrophy, and Fabry's syndrome.